With the advancement of a public communications network such as the Internet, the traffic volume between terminal devices such as computers and smartphones and server devices that distribute data such as digital contents to the terminal devices is increased. The digital contents include, for example, websites, video data, music data, and software.
Since the electric power consumption of networking equipment such as routers and server devices is increased with an increase in traffic volume, a reduction in the volume of traffic flowing through the network is desired. In response to this, a technique of reducing the traffic volume by holding cache data (replica) of digital content in a plurality of routers and distributing the cache data from a router of a node close to a terminal device has been known (see Japanese Laid-open Patent Publication No. 2013-183241 and Satoshi Imai et al., “Energy Efficient Content Locations for In-Network Caching”, In Proc. of Asia-Pacific Conference on Communications, Jeju, Korea, 2012). On the other hand, since the use of a storage is expected to be increased in the future due to holding of the cache data, the realization of cache data placement determined with consideration given to the relationship between a reduction in traffic and the holding amount of the storage becomes important.
Such a technique is called “content centric networking (CCN)” or the like, and a cache node used in CCN is called a “content router (CR)” or the like. For example, in CCN, an operational method such as deriving appropriate placement of cache data in the network in order to reduce consumed power with consideration given to the consumed power caused by caching digital content in memory, the cost of memory, the consumed power caused by distribution of digital content has been studied. In so doing, information such as a list of all the contents in the network and the distribution of requests for the content is also used.
Moreover, in Satoshi Imai et al., “Energy-Aware Cache Management for Content-Centric Networking”, in Proc. of First International Workshop on Energy-Aware Systems, Communications and Security, Barcelona, Spain, March 2013, a technique of controlling the efficient cache data placement by performing autonomous distribution processing in each node to facilitate the management of content information in the whole network in the CCN technology is disclosed. In this autonomous distribution processing, an appropriate threshold value of a request rate used to determine whether or not to perform caching is derived in order to reduce consumed power with consideration given to the consumed power caused by caching digital content and the consumed power caused by distribution of digital content.